Refining of oils



Patented Oct. 18, 1938 2,133,691

UNITED STATES PATENT OFFICE REFINING OF OILS Alfred W. Francis, Woodbury, N. .L, assignor to Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York No Drawing. Application June 27, 1936, Serial No. 87,764

3 Claims. (Cl. 19613) This invention relates to the refining of pethe control is efiected by modification of the setroleum, and has to do particularly with the lective solvent power of said liquid solvents by refining of petroleum fractions by processes of dissolving therein different or varying amounts selective solvent extraction. of appropriate inor ani compounds- 5 An example of the type of process with which The most important advantage of such a 5 this invention is concerned is that of fractionprocess pr b y Consists in the discovery a ation as between paraflinic and naphthenic the selectivity of normally poor solvents not compounds of like boiling range, but of different only may be increased to a very desirable degree, chemical and physical characteristics, to effect a but that a great flexibility of processing is thereseparation of the compounds of a paraflinic by provided, since concentrations of the inor- 10 nature from the compounds of a non-parafiinganic compound in the solvent may be varied to lo or naphthenic nature by means of a sesuit any desired extraction temperature. lective solvent showing different solvent powers a p es of the d fied S vent reagents fo th two clas of hydrocarbons, solutions which may be thus used, are solutions The effectiveness of such a fractionation or of the chlorides of cobalt, nickel, mercury (ic), 15

separation operation as that above described, and lithium in pyridine, lithium iodide or bromay be measured, and is measured herein, by mide in pyridine, lithium acetate in pyridine, the viscosity-gravity-constant or so-called V. G. C. calcium nitrate in pyridine, lithium chloride, This viscosity-gravityconstant, proposed by bromide, or iodide in butyl alcohol, isoamyl al- Hill and Coates, Ind. and Eng. Chem. 1928, page cohol, tertiary amyl alcohol, or ethyl alcohol, 641, is a valuable indication of the paraffinic solutions of lithium chloride, bromide, or iodide nature of an oil fraction, since the said V. G. C. in acetone, solutions of zinc chloride in ethyl value indicates increasing freedom from constiacetate, ethyl ether, or dimethyl aniline, solutuents highly naphthenic with decrease in nutions of lithium chloride, calcium nitrate, cobalt merical value of the constant. The V. G. C. for chloride, mercuric chloride, zinc chloride, lithv25 present-day lubricants of Pennsylvania origin, ium bromide, lithium iodide, or lithium acetate (not solvent refined) is around 0.800 to 0.830, in picoline, solutions of lithium chloride in cre- W h similar lubricant frac ions from o her sylic acid, solutions of mercuric chloride in butyl Sources ranging p t 0900- cellosolve, solutions of perchlorates in some or- An important Oblect of thls mventlon 1s a ganic solvents, and solutions in acetone of mer- 30 novel method'fo'r the P of petroleum curic chloride or of the sulphocyanates of sofractions of similar boilingpoints, etc., but of dium, potassium or ammonium ven an sa t is e ec ive in which the salt dis Solvents modlfied by the presence of morgamc solves in the solvent to a suflicient extent to salts.

It is a further object of this invention to affect the selectivity of the solvent, provided the Vide novel refining agents for the above salt is substantially non-reactive to oil and solposes, and to improve known liquid selective solvent remams in solutlen in Su a 40 Vent agents f this purpose, and to provide a amounts in the presence of oil. Spec1fic exam- 40 process for using these novel and improved ples of suitable salt-solvent combinations which lective solvent agents I have found, up to the present, to be useful for One object of this invention is to provide a thls purpose, are the Sollltlons of lithium c 0- process of refining petroleum lubricant stocks l l Q i e 0f e l trat which is applicable generally to any petroleum m Y P 18 a d Combinations there- 5 lubricant oil stock which contains fractions of of, provlded they mutually inertgood lubricating n b t also contains asphal- To show the effectiveness of these salt-solvent tic and/or naphthenic matter to produce theremodlfied Solvent reagents for the purposes from refined lubricating 11 of high quality indicated, an example is here noted wherein an r having a good viscosity-gravity-constant and oil was extracted with four times its volume of a 50 other desirable qualities. 5% solution (about saturated) of lithium Amost important object of this invention is to chloride in py a C- The sult n provide a process of this nature which is adaptwo lay were Separated- The ppe 01 O l able for controlling the effectiveness and selecy r Was en c ol d to a u resulting tivity of said selective solvent agents, wherein n the S p a on o an additional t a layer 55 which was added to the original solvent layer. The oil layer contained some pyridine, which was removed by distillation, (leaving only a trace of lithium chloride), leaving a raflinate of increased value, as shown in the tabular data inserted below. The extract layer was distilled to separate the pyridine therefrom and the oil removed from the residual salt by decantation.

In a second example, another portion of the same oil stock was treated twice successively with two volumes each of a 4% (about half saturated), solution of calcium nitrate in pyridine at 50 C. The lower layer was withdrawn, distilled, and decanted as above to recover the pyridine and salt. The upper layer, or raflinate, was heated to remove pyridine by distillation.

The properties of the original oil and of the two raflinates are shown in the following table:

It will be noted that the treatment resulted in a greatly improved raffinate. The two extractions are about equally efficient, but it should be observed that the calcium nitrate-solvent procedure involved a double extraction and that the lithium chloride-solvent procedure involved a higher temperature, which permitted a higher molar concentration of the salt. It .should be noted also that if pyridine alone is used as the selective solvent, a temperature of below 0 C. is ordinarily necessary to cause separation into two layers. and the improvement of the rafiinate under these conditions is very much less.

Calcium nitrate in pyridine cannot be used at much higher concentration or temperature than shown .above without precipitation of the salt, resulting in the mixing of the two layers. Lithium chloride in pyridine can be used up to about 120 C. and 7% concentration, with some increase in selectivity of the selective solvent.

The salt, solvent, concentration and temperature chosen-should be such that the salt remains in solution in the solvent under conditions of treatment, as pointed out hereinbefore.

In the following claims, the term solvent refining is used to designate the fractionation of petroleum fractions to separate constituents of varying chemical properties by means of a sol vent having selective solvent power for one of the classes of constituents.

I claim:

1. In the refining of petroleum fractions by means of a selective solvent, without substantial chemical change of oil constituents, the method which comprises the following steps: dissolving in said solvent a small amount of a solvent-soluble inorganic salt selected from the group of solvent-soluble salts consisting of lithium chloride, lithium bromide, lithium iodide, lithium acetate, the said selective solvent being selected from the group of selective solvents consisting of pyridine and picoline, mixing a sufficient amount of the modified solvent with oil to permit the formation of two oil-containing phases, effecting separation into a parafi'mic rafllnate phase and a naphthenic extract phase, separating the phases,

and recovering solvent-free, salt-free oil from the Y separated phases.

2. In the method of the refining of petroleum fractions by means of a selective solvent comprising pyridine, the steps which comprise dissolving lithium chloride in the pyridine, mixing the pyridine solution of lithium chloride with the oil to be refined, effecting the formation of a parailinic raffinate and a naphthenic extract phase within the mixture thus obtained, separating the said phases, and freeing the rafilnate phase of solvent .1

and salt to form a refined oil of greater paraffinicity.

3. In the method of solvent refining lubricant oils by means of a selective solvent comprising pyridine, the steps which comprise dissolving in the pyridine about 5% of lithium chloride, mixing the pyridine solution of lithium chloride with oil to be refined at a temperature of about 100 -C., efiectng formation of paraffinic raflinate and naphthen-ic extract phases from the mixture so obtained, separating the phases, and, freeing the raffinate phase of solvent and salt to form a. refined oil of lower viscosity-gravity-constant.

ALFRED W. FRANCIS. 

